This invention relates in general to a boosted air engine, for example a supercharged or turbocharged engine, and, more specifically to an engine having both an ambient air induction port and a charged air induction port.
Supercharged, that is, boosted air engines induct air at greater than ambient pressures into the combustion chamber to deliver a greater amount of air-fuel mixture to the engine and thus provide more power for a given engine size and speed. Typically engines are supercharged by use of a turbocharger or a mechanical supercharger. A turbocharger uses exhaust gasses to drive a turbine that, in turn, drives an air compressor. Turbochargers can both increase power and mileage. A typical mechanical supercharger is belt-driven by the engine crankshaft and is of a displacement blower type that produces a constant displacement of charged air with a given engine speed. Typically, superchargers boost air by 8-16 psi.
Most conventional boosted-air engines rely solely on boost air induction. The disadvantages of this are discussed in the prior art, the most common of which is the low efficiencies from turbochargers at low engine speeds and the slow response time to spool up the turbine to achieve maximum power. A conventional turbocharger relies on exhaust gas expanding to about 120% intake gas volume to power the turbocharger. With efficiency and pumping losses, there is little power left over to spool up the turbocharger and get the engine to speed up quickly.
Therefore, there has been a need for an improved supercharged engine, particularly one that takes advantage of normally aspirated air so that only the boost air portion need be supplied so as to reduce the work required by the supercharger.